I just finished an entry for the SOA timeline on the 1970s discovery that nematodes collect inactive enzymes and molecules as they grow older. The main idea being that the body is unable to clear out the junk inside cells and that the energy cost of carrying this junk leads to senescence, or aging.
The theory reminded me of a similar finding by Coleen Murphy who found that long lived daf-16 elegans mutants lived longer in part because they encoded antimicrobial lysosomes, that helped to clear out microbes that would get "packed" inside the nematodes precipiating senescence and eventually their death.
As far as I know, the reason for the slow decline in enzyme activity and for the collection of intracellular junk is still unknown. Why isn't our body clearing this stuff out and selling it on ebay? The SENS foundation, which is perhaps the biggest player in anti-aging research, is pushing forward with a solution anyway. Their strategy is to find enzymes manufactured by soil bacteria and fungi that can then be applied therapeutically to help clear junk out of cells. Such similar medications have already been discovered for people with Gaucher's disease.
It is going to be interesting in the future to see what result comes of this. Both for understanding the chemical mechanism of the collection of junk, and the therapeutic solutions which can get rid of it.
Harriet Gershon, & David Gershon (1970). Detection of Inactive Enzyme Molecules in Ageing Organisms. Nature 227, 1214-1217
Murphy, C., McCarroll, S., Bargmann, C., Fraser, A., Kamath, R., Ahringer, J., Li, H., & Kenyon, C. (2003). Genes that act downstream of DAF-16 to influence the lifespan of Caenorhabditis elegans Nature, 424 (6946), 277-283 DOI: 10.1038/nature01789
